1. Field of the Invention
The present invention relates to a machine for exchanging a group of at least old tie for of a group of at least one new tie in a railroad track consisting of two rails fastened to ties, which comprises a self-propelled standard railroad vehicle comprising a machine frame, undercarriages supporting the machine frame for mobility on the railroad track, and a drive for advancing the vehicle in an operating direction. A tie exchanging device is connected to the machine frame and is operable for withdrawing the old ties and inserting the new ties. This device comprises a longitudinally adjustable tie gripping means including a tie clamp, a drive for longitudinally adjusting the tie gripping means, and respective drives for vertically adjusting and for operating the tie clamp between tie engaging and tie releasing positions.
2. Description of the Prior Art
U.S. Pat. No. 4,253,398, dated Mar. 3, 1981, discloses a mobile apparatus for the continuous sequential replacement of all old ties of a track with a track renewal train which removes all the old ties and lays the new ties while the track rails are lifted and spread apart.
U.S. Pat. No. 4,611,541, dated Sept. 16, 1986, discloses a continuously advancing ballast cleaning machine with tie replacement devices, wherein the ballast is excavated, cleaned and returned while the track is raised a substantial amount. The tie pulling and inserting devices are mounted between the swivel trucks supporting the respective ends of the ballast cleaning machine frame and are connected to longitudinal displacement drives. These devices are used only when an obstacle hindering the operation of the ballast excavating chain is encountered on the shoulder of the track, i.e. they are merely auxiliary means in the ballast cleaning machine for occasional use. No control or control cab for operation of the auxiliary tie replacement devices is indicated.
It is also known, and has been widely practiced, to exchange only groups of ties in an existing track, for example every third or fourth tie or groups of adjacent ties between ties retained in the track to enable the same to support rolling stock traveling thereover, which is the technology to which the present invention relates. Such a partial tie exchange or renewal is repeated every few years until all the ties of the track has been replaced. Such a mechanized tie gang has been described on pages 22 to 24 of "Railway Track and Structures", November 1983. This mechanized tie gang comprises up to 24 pieces of equipment, such as tie cranes, spike pullers, tie shears, tie cranes for handling tie butts, rotary scarifiers, tie injectors, tampers, rail lifts, spikers and ballast regulators. In the operation of this tie gang, the old ties are withdrawn and placed on the shoulders of the track after optionally being sawn into chunks and they are then loaded onto railroad cars. The new ties are placed on the track shoulders for insertion. The loading and unloading of the ties may be effected at a different time than the tie exchange operation.
Commonly assigned U.S. applications Ser. Nos. 97,757, 97,759 and 97,760, all filed Sept. 17, 1987, disclose a mobile tie replacement apparatus which comprises at least one elongated bridge-like work vehicle having two undercarriages supporting respective opposite ends of the work vehicle on the railroad track, and a succession of different individual devices mounted on the work vehicle or vehicles between the undercarriages and operative to effectuate different sequential operations for exchanging the selected old ties for the new ties. The present invention provides specific improvements in such an apparatus.
Many tie exchange devices of different structures are known, which have a crane or cantilevered frame structure equipped with a tie clamping head. For example, U.S. Pat. No. 4,579,060, dated Apr. 1, 1986, discloses a tie exchanger with a compound clamping head. A pivotal crane is mounted on a forwardly projecting frame portion of a work vehicle, and an end of the crane carries a hydraulically operable tie gripping means with a tie clamp. The outrigger crane is relatively bulky compared to the frame of the work vehicle, which makes the structure unstable and, on the other hand, quite expensive. In addition, pulling or inserting a tie is relatively difficult since at least one of the undercarriages of the work vehicle rests with its full weight on the track in the immediate area of the tie exchange. The compound clamping head simultaneously grips a new tie and an old tie to enable the old tie to be withdrawn and the new tie to be inserted in two sequential stages. This makes the tie exchange even more difficult for the operator. More particularly, the uneven load exerted by the outrigger crane at one side of the vehicle makes an accurate, rapid and trouble-free tie exchange at least uncertain if not impossible. The device can be used only for the exchange of one tie at a time, and the old ties are usually placed on the track shoulder where the new ties also are stored ready for insertion. The productivity of such a tie exchange apparatus is quite limited. Moreover, such small work vehicles usually do not have their own drive and can be moved along the track only at low speeds.
Another type of tie exchanging apparatus is disclosed in U.S. Pat. No. 4,418,625, dated Dec. 6, 1983. This apparatus comprises a standard railroad vehicle comprising a horizontally extending machine frame and undercarriages supporting the machine frame for mobility on the railroad track. An extensible telescoping beam assembly carrying hydraulically actuated tie clamping arms on the opposite, remote ends is mounted on the machine frame between the undercarriages so that the tie gripping means are longitudinally adjustable and the tie clamps are also vertically adjustable. Alternatively, the tie exchanger may be mounted on a turret to permit controlled rotation about the vertical axis for operation on either side of the machine frame. No operator's seat or cab is provided on the frame within view of the tie gripping means so that the tie exchange operation may neither be observed or controlled from the vehicle. Presumably, an operator standing next to the track remote-controls the tie exchange. This apparatus, too, has a low productivity and only limited accuracy, particularly in view of the operating difficulties involved in the stop-and-go advance of the machine. The arrangement of the telescopingly extensible beam assembly carrying the tie gripping means under the horizontally extending machine frame provides very little space for the tie exchanging device.